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Discussion Starter #1
Does anyone know of a complete guide to the S4 Motronic system?

I'd like to know more about how it works, how it is programmed, how it adjusts settings for different situations etc.
 

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Hi Nick

I have always used this Opel/GM motronic ML4.1 guide to get a decent understanding how things work (or should work!)
Some things have a different name but easy to work out.

Happy new year btw!!
Dom
 

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But Mad North-Northwest
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The Probst book "Bosch Fuel Injection and Engine Management: How to Understand, Service and Modify" is also a good resource.
 

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Discussion Starter #4 (Edited)
Thanks Tom and Dom.

I have ordered the book and downloaded Dom's pdf so looking forward to some light reading!

Happy New Year to you too! (and all the other folk on the BB)
 

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Bosch Fuel Injection

Hello AngloSpider,

Here's an excerpt from a book I came upon a while back that I don't believe I have seen on our site before. It discusses the entire range of Bosch FI systems, and also goes into a lot of detail on fundamentals.

http://www.tonybmw.co.uk/Downloads/Bosch_Fuel_Injection.pdf

Table a. is in error regarding Motronic in Alfas from 85-89, but that's a minor quibble.

All the best.
 

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Discussion Starter #8 (Edited)
Thanks Greg. I had found that article using Google before I posted the query, but didn't realise it was written by you. I will read it even more attentively now I know its from somebody who knows Alfas so well :thumbup:

I guess what I won't get from these articles and books is any specific information about how the Motronic in the S4 is set up.

For example, the P/N for the ECU is the same for my S4 manual car, which had no cat, as it is for the automatic car which, as well as the auto box, had a cat fitted. The wiring diagram shows what looks to be a jumper for manual/automatic but doesn't say what it does when it is connected. Does it change the driving characteristics (more torque, less power or vice versa) or influence when the auto box changes up/down?

Also, one of these guides suggests that when a sensor goes bad, the default setting is that of a hot engine, so the car might be harder to start when cold. This appears to contradict the accepted wisdom that says a missing or bad lambda probe will put the car into an over-rich running mode. Or am I getting confused (it happens!)?
Given that the P/N for the ECU is the same for cat/non-cat, I am guessing that the connection of the Lambda probe lets the ECU know it needs to take it's readings into account. So, wouldn't disconnecting it fully just put the ECU into a non-cat equipped car state?
I would like to get a clear picture on the lambda probe as I currently have one on the automatic car, despite having got rid of the cat, and would like to lose it altogether if I change the exhaust.

As you can see, the Christmas break has made work for an idle mind and I'm just curious!
 

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But Mad North-Northwest
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Well if you read the book I posted, you'll probably learn that you want to keep the lambda probe even without the cat.

People think of it as an emissions device, but it's really a tuning device: it lets your engine self-correct the mixture for best running at cruise and idle. At full throttle the system goes open loop (ignores the lambda sensor output) and enrichens the mixture for more power, so you're not losing anything by keeping it.

Even without a cat, having the oxygen sensor is a good thing.
 

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Discussion Starter #10
That's an interesting point.
But triggers the next question:p - I wonder why they didn't put one on the non-cat cars that they were selling in Europe at the time they were selling the cat ones in the US? Cost, I guess.
 

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That's an interesting point.
But triggers the next question:p - I wonder why they didn't put one on the non-cat cars that they were selling in Europe at the time they were selling the cat ones in the US? Cost, I guess.
Nick,
what I have noticed is that although our ECUs are all Bosch p/n 0 261 200 124 (same as alfa 75 1.8 ie, according to Bosch), there are further markings on the white paper label with the barcode on it, and I just wonder if those particular markings differentiate between a cat and non-cat model?
Have you looked at yours to see if both your manual and auto (or Cat and non-Cat) S4 have a different number on the white label?

Photo 1 shows mine (002/810) on my euro S4 spider with Cat
Photo 2 is an S4 spider ECU for sale on the web with an 003/810 label

I might be wrong in my assumption, but it is odd nonetheless!
 

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Discussion Starter #12
The plot thickens! I haven't checked the one in the automatic yet but I have a spare one from a non-cat manual car and that has an 003/810 label.

Does the ad for the one for sale state what model it is from?
 

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The plot thickens! I haven't checked the one in the automatic yet but I have a spare one from a non-cat manual car and that has an 003/810 label.

Does the ad for the one for sale state what model it is from?
just says 'Spider S4 1990 -1993; also fits alfa 75 1.8ie according to Bosch'
It was a German ad. and afaik German S4s always came with Cat., but you never know if it came off an import car (UK, Italy, Portugal whatever)

I was just back there to check and clean all the ECU pins and main feed block on the ECU mounting plate.....mine was all dusty (now nice 'n clean;)) so certainly seems original to my car (my car is a fairly early German S4, May 1990)
 
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